Method for treating aluminum or aluminum alloy scrap



Dec. 25, 1945; M. STERN 2,391,752

METHOD FOR TREATING ALUMINUM OR ALUMINUM ALLOY SCRAP I Filed May 30, 1942 IN VEN TOR:

PotentedDec. 25, ess.

mm srAras PATENT forrlcs I a m ma: smnew N. r. Application my so, 1942, Serial No. 445.19g

K a cl. 201-) The inventionrelates to amethod for the treatment of aluminum or aluminum alloy scrap or waste and particularly for the direct production of finished articles therefrom; it is a continuation in part oi my patent application Ser. No. 356,665, which has matured into Patent No.

It also relates to the direct manufacture by ex-- trusion, pressing, rolling and similar mechanical pressure operations of tube, rods, sheets, cupshaped bodies, structural profiles such as T- shaped, U -shaped and I-shaped profiles from aluminum or aluminum alloy turnings, borings, chippings, filings, grindings or clippings.

The utilization and compression of metal scrap and also aluminum scrap into briquettes and packetstor remelting purposes is an old expedient and so is the direct manufacture of finished articles from preheated aluminum or aluminum al- 10y insots.

It maytherefore be understood that the present invention exclusively relates to the direct pressure conversion of aluminum scrap or waste into the finished article.

This direct conversion of aluminum borings,

chippings, filings, grin, clippings and turnings into finished articles presents severe and specific dimculties and therefore has not been attempted as yet. 7

Aluminum scrap and waste generally contains organic contaminating substances and water. The scrap must be completely cleaned and dried before it may be extruded or shaped by mechanical pressure methods.

If this is omitted the inter-sec oil and water films will prevent a union of the scrap particles and their coalescence into homogeneous bodies.

However, the most severe culty in the mechanical pressure shaping of aluminum and aluminum alloy scrap and waste into finishedhodies is created by the presence of oxidic filmsof a very tough and resistant nature which encase the individual scrap and waste particles and pieces and strongly adhere thereto.

Articles manufactured from the scrap by a method whereby these oxide skins are not dierupted and scattered or dispersed within the material under pressure have little coherence and strength because the oxide films prevent the metallic contact of the individual scrap particles and their union into uniform metallic bodies. These difficulties are not overcome by raising the pressure to an even exceedingly high rate.

This phenomenon explains why aluminum scrap and waste has up to now only utilized by remelting which as "generally known. involves heavy metal losses. Furthermore. it is known that the so-called secondary or remelted ingots cannot be extrudedor rolled unless they are pre- 7 viously refined or mixed with virgin metal.

The seve e objections to the direct manufacture of ed articles from every type of aluminum and aluminum alloy scrap and waste hymechanical pressuremethodsare obviated by the present invention; the latter is based upon the recognition that a temperature of at least about 300 C. must be maintained during the pressure operation in order to loosen the oxide skins which not any more supported by the softened metal, are disrupted by thepressureexerted thereupon and dispersed within the scrap under treatment thereby oifering fresh metallic contact faces throughout the latter. s

It therefore is the object of this invention to convert aluminum and aluminum alloy scrap and waste directlyinto finished articles by mechanical methods. i

A further object of the invention is to avoid remelting of the scrap and the large metal losses as caused thereby.

It is also an object of the invention to preserve the properties and the structure of the primary metal; as clippings, turnings and other types or scrap mainly originate from the virgin metal the scrap bodies made in accordance with the invention may be directly worked in rolling, extruding and forging apparatus;

It is another important object of the invention to recover practically the entire metal contents of the scrapas a finished article having a uniform fine grained structure and good mechanical properties.

It is a'further object of the invention to loosen the oxide films. enveloping the scrap and to disrupt the same and to hereby promote a metallic union of the scrap particles whereby coherent homogeneous articles are obtained which substantially have the mechanical properties and the corrosion resistance of the virgin metals.

Therefore. according to this invention, the aluminum scrap or waste is freed from contaminatins organic substances and water and directly converted by extrusion or other mechanical pressure methods at a temperature of at least about so 300 0. into the shape of the final article.

so is between 18 to 40 tabs per square inch; lower acorns:

' Several modifications of ca ng out thisln vention aredescribed in'the following: -(1) Duralumin turnings are freed from their organic contaminations such as oil by a. suitable 7 method! Hereupon the iron is preferably separated from the scrap by a magnet.

The thus treated turnings are heated to a temperature of at least 300 C. The hot scrap is charged into an extrusion press which is provided with a heated container. The scrap is finally extruded at a temperature or between 300 to 450 C. and at a pressure of about between 18 to 40 tons per square inch into rods. tubes or structural profiles of usual cross section. The oxide films which are not more sufilciently supported by the softened metal are additionally disrupted by the pressure and forming force exerted upon the compressed scrap and a homogeneous union is effected of the scrap particles through the entirely dispersed oxide skins which remain uniformly dist.ibuted in the compressed body and do not reduce the uniformity and coherence oi the same.

In this manner a finished article is produced from the aluminum scrap which in a mechanical and chemical respect is sufilciently resistant to be employed for most purposes for which a high grade aluminum or aluminum alloy is used.

(2) -Aluminum borings are heated to a temperature of between 200 and 300T 0., hereby freed from oil and dried.

The thus treated borings are compressed in a hydraulic press at a pressure or about 3 to 8 tons per square inch and a temperature 01 about 300 G. into coherent bodies; the loosened omde skins are hereby disrupted and'uniiormly scattered.

These bodies are charged into an extrusion press and extruded at a temperature or at least 300 C. and preferably 350 to 450 C. and at a pressure of about 18 to 40 tons per square inch into final articles. 4

(3) Duralumin chippings after being cleaned, freed from organic contaminations and dried are directly charged into the cylinder of an extrusion press which is heated. The scrap is compressed at a temperature of about 300 C. and a comparatively low pressure; the pressure is graduallyincreased to about 18 to 40 tons per square inch and the temperature raised to 350 to 450 0.: the scrap is hereby extruded into the final article.

The thus produced articles have a uniform finegrain structure obtained by the specific working conditions oi the present tically equal as far as their mechanical proper. ties and their structure is concerned, to articles extruded or rolled from virgin metal ingots.

An extrusion die for carrying out a preferred method is shown by way oi. example in the attached drawing. or which method: they are prac- Fig. 1 illustrates the operating position of th die after the hot scrap has been charged into th: pressing space. and r V Fig. 2 illustrates its position when the extru sion commences.

The die comprisesan extrusion cylinder 0 am a piston b movable in the cylinder; an aperturi o is provided in the bottom member m. The loos: scrap charged into the pressing space or the die is indicated by d. Bottom plate e end rod section 1 which close the pressing space indicate the remnants oi the article produced by a previous pressing stage. 1

In accordance with the operating position shown in Fig. 2 the primarily loose scrap d is compressed by the downward movement of piston b and converted into coherent body n; by continued movement of the piston b and increase of the pressure to such a degree as is necessary to perterm extrusion, body 11. is extruded whereby the metal rod is formed as a finished article.

Various changes may be made to the method steps set forth in this description in connection with extrusion or other shaping methods without departing from the broader spirit and scope of the invention, as set forth in the following claims. Iclaim: 1 1. Method of producing final articles, for instance tubes, rods and structural profiles from aluminum and aluminum alloy scrap comprising compressing the scrap by maintaining the same at a temperature of about 300 C. and at a pressure of approximately 3 8 tons'pcr square inch, disrupting thereby the oxide skins coating the scrap particles and creating fresh metallic contact faces, thereupon increasing the temperature to about 350 to 450 (2. and the pressure to about 18-40 tons per square inch and converting said bodies by maintaining these conditions directly into the final articles.

2. Method of producing final articles, for intance tubes, rods and structural profiles from aluminum and aluminum alloy scrap comprising compressing the scrap by maintaining the same 0. and at a presbodies by maintaining these conditions directly into the final articles.-

3. Method 01' producing final articles, for instance tubes, rods and structural profiles, from aluminum and aluminum alloy scrap, comprising gggfing the scrap to a temperature of at least ing device and shaping the same at a sure 01' about between 18 to 40 tons per square inch into the final articles.

MAX STERN.

C., charging the heated scrap into a pressfinal pres- 

